Baroclinic Torque and Implications for Subgrid-Scale Modeling

Baroclinic torque plays an important role in the dynamics of variable-density flows. Large eddy simulations using Favre-filtered resolved-scale velocities mask the explicit dependence of resolved-scale dynamics on subgrid-scale pressure-gradient-density interactions. The effect of subgrid-scale baroclinic torque on resolved scales is implicitly included in the subgrid-scale stress and subgrid-scale scalar fluxes through the resolved-scale vorticity it generates. LES closure models must therefore incorporate this effect in the computations. We explore the physics of subgrid-scale baroclinic torque within the structural framework of the Stretched-Vortex model. Fine-scale simulations of supersonic flows and direct numerical simulations of variable-density turbulence are investigated. Such flows have regions of active baroclinic torque and serve to set up flow configurations to assess the model.